Oar blade or the like



Dec. 30, 193.0. J. L. RIBARD 1,786,451

OAR BLADE OR THE LIKE Filed June 1, 1928 my W 4770/091 Patented Dec. 38,1930 UNITED STATES JEAN LOUIS RIBARD, F PARIS, FRANCE OAR BLADE OR THELIKE Application filed June 1, 1928, Serial No. 282,203, and in FranceJune 10, 1927.

The present invention has for its object 1 an improvement in oar bladesor like surfaces which are subjected to the thrust of a fluid,

and the improvement consisting in forming 5 in an oar blade or the likeholes having the shape of a truncated cone of which the larger base isplaced on the side where the fluid exerts its thrust.

I have discovered that the presence of these apertures, far fromdiminishing, as might be thought, the total pressure acting upon thesurface, has on the contrary, the result of increasing this pressure. Itis probable that this effect is due to the fact that the fluid streams,meeting the lateral surface of the truncated cone, are engulfed thereinand can no longer flow away except by way of a restricted orificethrough which they are wire-drawn. The deviation of the streams towardsthe edges of the surface, would thus be reduced to a large extent,leading to a reduction of the eddies and losses resulting therefrom.

In the accompanying drawings, Figure 1 represents a front view of an oarblade, Figure 2 a section along the line 22 of Figure l and Figure 3 ananalogous section of a modification.

There is formed upon the forward or active wall of the blade a (takingcare to keep away from the rather fragile edges) a series of truncatedconical holes 6. These holes, ar-

ranged in the form of a quincunx in order to avoid weakening too far thefibres of the wood, have on an average a diameter of one centimetre atthe base and of about one millimetre at the apex. The number of theseholes must be as large as possible and has no limit other than thestrength of the blade to resist fracture.

Tests made with racing oars of which the blade comprised 36 of theseholes have shown that there was obtained an extremely clear increase ofspeed as compared with that obtained with ordinary racing oars.

In the case of oars adapted to be utilized on both faces, it isadvisable to give to the holes the shape of two truncated cones copposed at their smaller bases, as shown in Figure 3.

This arrangement can moreover be utilized even in the case where thewall is not called upon to receive the thrust of the fluid upon one orthe other of its faces, the double truncated cone then acting in themanner of a convergent divergent orifice.

The dimensions given above are, of course, not in any way limitative,but may vary according to the particular application. The same appliesas regards the shape of the right angle section of the truncated cones.

My invention is applicable to other elements or surfaces which aresubjected to the thrust of a fluid.

What I claim is:

An oar blade having longitudinal rows of openings therein, thecorresponding openings in relatively adjacent rows being relativelylongitudinally offset, and the said openings each having the form of twotruncated cones meeting at their smaller ends.

In testimony whereof I have signed my name to this specification.

JEAN LOUIS RIBARD.

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